PITTSBURGH >> A prosecutor urged jurors today to focus on a white police officer’s frame of mind when he shot and killed an unarmed black teenager near Pittsburgh last summer.

Former East Pittsburgh Police Officer Michael Rosfeld, 30, fired three bullets into 17-year-old Antwon Rose II after pulling over an unlicensed taxicab suspected to have been used in a drive-by shooting minutes earlier. Rose was a front-seat passenger in the cab and was shot as he fled.

Prosecutors said Rosfeld, who was charged with homicide, gave inconsistent statements about the shooting, including whether he thought Rose had a gun.

“What really, really matters is what Michael Rosfeld knew and what he believed and what he thought when he pulled the trigger,” Deputy District Attorney Daniel Fitzsimmons told jurors in his opening statement.

Defense attorney Patrick Thomassey said Rosfeld did not intend to shoot anyone that day and did nothing wrong in his fatal encounter with Rose.

“You think Michael Rosfeld got up on the 19th of June and thought he was going to shoot someone? Of course not,” he said.

The shooting was captured on video by bystanders and posted online, triggering protests in the Pittsburgh area last year, including a late-night march that shut down a major highway.

A jury of six men and six women, including three African-Americans, was selected across the state in Harrisburg last week and will be sequestered in a Pittsburgh hotel for the duration of the trial, expected to take a week or more.

The families of Rose and Rosfeld were in the courtroom today as the trial got underway.

“Antwon’s family is here seeking the justice they so deserve and to assure that the light of Antwon’s memory shines forever,” said a statement issued today by the family’s lawyer, Fred Rabner, who represents them in a wrongful death suit against Rosfeld, the borough and its mayor and police chief. The family statement called Rosfeld “hair-triggered” and “overly aggressive,” adding that his gun had “left an irreparable hole in their collective souls.”

Rose had been riding in the front seat of an unlicensed taxicab when the backseat passenger rolled down a window and shot at two men on the streets of North Braddock.

The shooter was Zaijuan Hester, 18, of Swissvale, who pleaded guilty Friday to aggravated assault and firearms violations for the shooting, which wounded a man in the abdomen. Hester told a judge that he, not Rose, did the shooting. A judge ruled Monday that jurors will hear evidence of that shooting but likely will not hear about a robbery that occurred several hours earlier.

Police Sgt. Brian Hodges of North Braddock testified today that he and Rosfeld responded to the drive-by, and that Rosfeld went in search of the car spotted leaving the scene. A short time later, Rosfeld pulled it over. While Rose ran from the vehicle, Rosfeld shot him three times — in the right side of his face, in his elbow and in his back — a bullet tearing through his heart and lung.

In its opening, the defense asserted that Rose was complicit in the drive-by shooting, identifying the target to the gunman, Hester. Rose had an empty ammunition clip in his pants when he was killed, and two handguns were recovered from inside the vehicle.

The prosecutor urged jurors to focus on what Rosfeld knew about any of that when he shot Rose.

Rosfeld initially told investigators that he saw something in Rose’s hand that Rosfeld thought was a gun, according to a police affidavit.

“This observation caused him to step from behind the cover of his car door to acquire a better view,” the affidavit said. “He then fired his weapon.”

Investigators have said Rosfeld subsequently told the detectives he did not see a gun when the passenger ran.

“When confronted with this inconsistency, Rosfeld stated he saw something in the passenger’s hand but was not sure what it was,” police wrote. “In addition, Officer Rosfeld stated that he was not certain if the individual who had his arm pointed at him was still pointing at him when he fired the shots.”

Rosfeld had been on the East Pittsburgh police force for just a few weeks after working for other departments over seven years. After the shooting, East Pittsburgh shut down its police force and began to rely on state police to cover the territory.